<!DOCTYPE html>
<html>
<head>
    <title>计算中...</title>
    <meta http-equiv="refresh" content="2">
    <style>
        body { text-align: center; padding: 50px; font-family: Arial; }
        .spinner {
            border: 5px solid #f3f3f3;
            border-top: 5px solid #3498db;
            border-radius: 50%;
            width: 50px;
            height: 50px;
            animation: spin 1s linear infinite;
            margin: 20px auto;
        }
        @keyframes spin {
            0% { transform: rotate(0deg); }
            100% { transform: rotate(360deg); }
        }
    </style>
</head>
<body>
    <h1>正在计算您的方程</h1>
    <div class="spinner"></div>
    <p>请勿关闭页面，计算完成后将自动跳转...</p>
</body>
</html>